Shove Vole

Shove Voles are Critters that live on the surface of the asteroid and can burrow (pass) through most tiles, and walk on walls and ceilings. The only exceptions are tiles made out of Refined Metal or of at least "Nearly Impenetrable" Hardness: Abyssalite, Insulation, Wolframite, Diamond, Neutronium, and Obsidian. It cannot burrow through Pneumatic Door of any material type.

Behaviour
They eat debris and excrete it as a solid tile but at a 50% loss of mass, renewing the asteroid's surface after meteors hit and destroy it. They can eat the whole item they find, even if it weighs 20 tons - they will eat it entirely and excrete a single tile with 10 ton mass.

Combined behaviours of Voles and Pips can be utilised to re-create regions with wild-growing plants.

Domestication
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Care should be taken when bringing them into a sub-surface stable as a source of meat.

Once unleashed into the asteroid, it is difficult to track them down, steel airlocks or Pneumatic Doors as the sole access are advised as well as metal or obsidian tiles wherever abyssalite is missing, plus Robo-Miners if you feed them. Note that airlocks have to be built from steel, as shove voles will pass through airlocks built from copper, aluminum or iron; pneumatic doors can safely be built out of any metal.

Critter Traps and feeders might be able to catch an escapee, someday.

While they may be able to burrow, they can not fly or use ladders. If space is not an issue, building a platform with a 2-tile wide gap separating it from other walls can stop Voles from escaping. However, the eggs that drop down still need to be collected and placed back on platform.

Tips

 * Shove voles are a fully sustainable food source that does not require feeding. One vole will provide 1075 kcal/cycle of meat or 1344 kcal/cycle of barbeque provided the eggs are incubated and voles are groomed.
 * A vole takes 4 cycles to incubate, 5 cycles to mature, and 5.88 cycles to produce an egg. Total time to produce an egg : 4+5+5.88 = 14.88 cycles
 * A vole drops 16,000 kcal on death: 16000/14.88 = 1075 kcal/cycle of meat.
 * A tamed vole will start with 43,200 kcal upon hatching.
 * If you can fully support your shove vole over long time, you can get an egg every 5.88 cycles, leaving yourself with 2721kcal/cycle of uncooked meat and 3401kcal/cycle if cooked to Barbecue.
 * One incubator will support 1.47 voles (if fed) or 3.72 voles (if not fed).
 * Because they drop so much meat (and thus barbeque) they can be used as an alternative food source for radiant bugs if diamond is in short supply or unavailable.
 * Viewing the navigation of a wild shove vole allows you to see the map (and determine the location of the pod if your seed has miscalculated pod location)
 * Shove vole does not get the overcrowded debuff.
 * Because shove voles do not get the overcrowded debuff, a small room stable can hold an arbitrarily large amount of shove voles. This number is limited to how quickly duplicants can groom and keep them happy. Care must be taken to avoid excessively large numbers as they will drop both meat and your frame rate.